Improve OutputsSpec slightly

A few little changes preparing for the rest.

src/libcmd/installables.cc

@@ -1,5 +1,6 @@
 #include "globals.hh"
 #include "installables.hh"
+#include "outputs-spec.hh"
 #include "util.hh"
 #include "command.hh"
 #include "attr-path.hh"
@@ -796,7 +797,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         }
 
         for (auto & s : ss) {
-            auto [prefix, outputsSpec] = parseOutputsSpec(s);
+            auto [prefix, outputsSpec] = OutputsSpec::parse(s);
             result.push_back(
                 std::make_shared<InstallableAttrPath>(
                     state, *this, vFile,

src/libexpr/flake/flakeref.cc

@@ -244,7 +244,7 @@ std::tuple<FlakeRef, std::string, OutputsSpec> parseFlakeRefWithFragmentAndOutpu
     bool allowMissing,
     bool isFlake)
 {
-    auto [prefix, outputsSpec] = parseOutputsSpec(url);
+    auto [prefix, outputsSpec] = OutputsSpec::parse(url);
     auto [flakeRef, fragment] = parseFlakeRefWithFragment(prefix, baseDir, allowMissing, isFlake);
     return {std::move(flakeRef), fragment, outputsSpec};
 }

src/libstore/outputs-spec.cc

@@ -1,3 +1,4 @@
+#include "util.hh"
 #include "outputs-spec.hh"
 #include "nlohmann/json.hpp"
 
@@ -5,7 +6,7 @@
 
 namespace nix {
 
-std::pair<std::string, OutputsSpec> parseOutputsSpec(const std::string & s)
+std::pair<std::string, OutputsSpec> OutputsSpec::parse(std::string s)
 {
     static std::regex regex(R"((.*)\^((\*)|([a-z]+(,[a-z]+)*)))");
 
@@ -19,18 +20,19 @@ std::pair<std::string, OutputsSpec> parseOutputsSpec(const std::string & s)
     return {match[1], tokenizeString<OutputNames>(match[4].str(), ",")};
 }
 
-std::string printOutputsSpec(const OutputsSpec & outputsSpec)
+std::string OutputsSpec::to_string() const
 {
-    if (std::get_if<DefaultOutputs>(&outputsSpec))
+    return std::visit(overloaded {
-        return "";
+        [&](const OutputsSpec::Default &) -> std::string {
-
+            return "";
-    if (std::get_if<AllOutputs>(&outputsSpec))
+        },
-        return "^*";
+        [&](const OutputsSpec::All &) -> std::string {
-
+            return "*";
-    if (auto outputNames = std::get_if<OutputNames>(&outputsSpec))
+        },
-        return "^" + concatStringsSep(",", *outputNames);
+        [&](const OutputsSpec::Names & outputNames) -> std::string {
-
+            return "^" + concatStringsSep(",", outputNames);
-    assert(false);
+        },
+    }, raw());
 }
 
 void to_json(nlohmann::json & json, const OutputsSpec & outputsSpec)

src/libstore/outputs-spec.hh

@@ -1,9 +1,8 @@
 #pragma once
 
+#include <set>
 #include <variant>
 
-#include "util.hh"
-
 #include "nlohmann/json_fwd.hpp"
 
 namespace nix {
@@ -18,13 +17,26 @@ struct DefaultOutputs {
     bool operator < (const DefaultOutputs & _) const { return false; }
 };
 
-typedef std::variant<DefaultOutputs, AllOutputs, OutputNames> OutputsSpec;
+typedef std::variant<DefaultOutputs, AllOutputs, OutputNames> _OutputsSpecRaw;
 
-/* Parse a string of the form 'prefix^output1,...outputN' or
+struct OutputsSpec : _OutputsSpecRaw {
-   'prefix^*', returning the prefix and the outputs spec. */
+    using Raw = _OutputsSpecRaw;
-std::pair<std::string, OutputsSpec> parseOutputsSpec(const std::string & s);
+    using Raw::Raw;
 
-std::string printOutputsSpec(const OutputsSpec & outputsSpec);
+    using Names = OutputNames;
+    using All = AllOutputs;
+    using Default = DefaultOutputs;
+
+    inline const Raw & raw() const {
+        return static_cast<const Raw &>(*this);
+    }
+
+    /* Parse a string of the form 'prefix^output1,...outputN' or
+       'prefix^*', returning the prefix and the outputs spec. */
+    static std::pair<std::string, OutputsSpec> parse(std::string s);
+
+    std::string to_string() const;
+};
 
 void to_json(nlohmann::json &, const OutputsSpec &);
 void from_json(const nlohmann::json &, OutputsSpec &);

src/libstore/path-with-outputs.hh

@@ -2,7 +2,6 @@
 
 #include "path.hh"
 #include "derived-path.hh"
-#include "nlohmann/json_fwd.hpp"
 
 namespace nix {
 

src/libstore/tests/outputs-spec.cc

@@ -4,40 +4,40 @@
 
 namespace nix {
 
-TEST(parseOutputsSpec, basic)
+TEST(OutputsSpec_parse, basic)
 {
     {
-        auto [prefix, outputsSpec] = parseOutputsSpec("foo");
+        auto [prefix, outputsSpec] = OutputsSpec::parse("foo");
         ASSERT_EQ(prefix, "foo");
         ASSERT_TRUE(std::get_if<DefaultOutputs>(&outputsSpec));
     }
 
     {
-        auto [prefix, outputsSpec] = parseOutputsSpec("foo^*");
+        auto [prefix, outputsSpec] = OutputsSpec::parse("foo^*");
         ASSERT_EQ(prefix, "foo");
         ASSERT_TRUE(std::get_if<AllOutputs>(&outputsSpec));
     }
 
     {
-        auto [prefix, outputsSpec] = parseOutputsSpec("foo^out");
+        auto [prefix, outputsSpec] = OutputsSpec::parse("foo^out");
         ASSERT_EQ(prefix, "foo");
         ASSERT_TRUE(std::get<OutputNames>(outputsSpec) == OutputNames({"out"}));
     }
 
     {
-        auto [prefix, outputsSpec] = parseOutputsSpec("foo^out,bin");
+        auto [prefix, outputsSpec] = OutputsSpec::parse("foo^out,bin");
         ASSERT_EQ(prefix, "foo");
         ASSERT_TRUE(std::get<OutputNames>(outputsSpec) == OutputNames({"out", "bin"}));
     }
 
     {
-        auto [prefix, outputsSpec] = parseOutputsSpec("foo^bar^out,bin");
+        auto [prefix, outputsSpec] = OutputsSpec::parse("foo^bar^out,bin");
         ASSERT_EQ(prefix, "foo^bar");
         ASSERT_TRUE(std::get<OutputNames>(outputsSpec) == OutputNames({"out", "bin"}));
     }
 
     {
-        auto [prefix, outputsSpec] = parseOutputsSpec("foo^&*()");
+        auto [prefix, outputsSpec] = OutputsSpec::parse("foo^&*()");
         ASSERT_EQ(prefix, "foo^&*()");
         ASSERT_TRUE(std::get_if<DefaultOutputs>(&outputsSpec));
     }

src/nix/profile.cc

@@ -44,7 +44,7 @@ struct ProfileElement
     std::string describe() const
     {
         if (source)
-            return fmt("%s#%s%s", source->originalRef, source->attrPath, printOutputsSpec(source->outputs));
+            return fmt("%s#%s%s", source->originalRef, source->attrPath, source->outputs.to_string());
         StringSet names;
         for (auto & path : storePaths)
             names.insert(DrvName(path.name()).name);
@@ -553,8 +553,8 @@ struct CmdProfileList : virtual EvalCommand, virtual StoreCommand, MixDefaultPro
         for (size_t i = 0; i < manifest.elements.size(); ++i) {
             auto & element(manifest.elements[i]);
             logger->cout("%d %s %s %s", i,
-                element.source ? element.source->originalRef.to_string() + "#" + element.source->attrPath + printOutputsSpec(element.source->outputs) : "-",
+                element.source ? element.source->originalRef.to_string() + "#" + element.source->attrPath + element.source->outputs.to_string() : "-",
-                element.source ? element.source->resolvedRef.to_string() + "#" + element.source->attrPath + printOutputsSpec(element.source->outputs) : "-",
+                element.source ? element.source->resolvedRef.to_string() + "#" + element.source->attrPath + element.source->outputs.to_string() : "-",
                 concatStringsSep(" ", store->printStorePathSet(element.storePaths)));
         }
     }